make it easier to handle application error responses

[ericgj]

Right now, if the request email coming in to your application isn't correct in some application-specific way, can't be parsed etc., your callback might look like

if valid?(request)
  ... 
  respond( ... )
else
  respond usage_response
end

Which is fine for simple cases, but if you have several different error conditions that each call for different behavior/responses, the code starts getting ugly with nested if's. One thing that might be helpful would be a way of exiting the callback early. You could use next -

unless valid_subject?(request)
  respond error_invalid_subject
  next
end

unless valid_body?(request)
  respond error_invalid_body
  next
end

... continue processing after validation passes

or to DRY it up, -

validate({:valid_body? => error_invalid_body,
          :valid_subject? => error_invalid_subject}) or next

... continue

But somehow that still isn't satisfying. Not suggesting rails-style controller validations, but maybe something Newman::Controller could help with that I'm not thinking of.

[practicingruby]

How about something like this?

validate do
  # check something about the message
end

invalid_request do
  # send a response, log it, etc.
end

A failed validation would set some state (or raise an error) which causes invalid_request to be triggered. This could also be done explicitly with some method that could be called from within any matcher. Better names are needed here.